CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - UNAUDITED - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 24,745	$ 54,800	$ 75,998	$ 98,735
Investments available-for-sale:
Net change in unrealized gains/ (losses) on investments available-for-sale	(13,609)	(38,857)	7,175	(104,780)
Related income tax (expense)/ benefit	3,466	9,961	(1,828)	26,858
Net investment gains reclassified into earnings	0	(38)	0	(46)
Related income tax expense	0	10	0	12
Net effect on other comprehensive income/ (loss)	(10,143)	(28,924)	5,347	(77,956)
Investments held-to-maturity:
Net change in unrealized gains/ (losses)	458	802	863	(15,127)
Related income tax (expense)/ benefit	(117)	(205)	(220)	3,878
Net effect on other comprehensive income/ (loss)	341	597	643	(11,249)
Defined benefit pension plan:
Amortization of net loss	226	195	451	391
Related income tax benefit	(58)	(50)	(115)	(100)
Net effect on other comprehensive income/ (loss)	168	145	336	291
Total other comprehensive income/ (loss)	(9,634)	(28,182)	6,326	(88,914)
Comprehensive income	$ 15,111	$ 26,618	$ 82,324	$ 9,821